Dome Z-Wave Water Main Shutoff Valve – $59.98 (plus tax)

Dome has Cyber Monday deals available on their website for 40% off including free standard shipping (plus tax, if applicable).
Enter the promo code "cybermonday40" at checkout for 40% off the Z-wave Water Main Shut Off Valve.
The deal runs through December 1st, 11:59 pm CST or while supplies last. They offer a few other devices such as water and motion sensors, but according to their customer service, it will work with Z-wave enabled smart home automation hubs. Therefore, no need to worry about buying other devices that are higher in price than other deals.